1. Field of the Invention
The present Invention relates to an IC card used, for example, as a credit card, a cash card, add the like.
2. Description of the Related Art
The conventional magnetic card, having a magnetic stripe for storing data, is in widespread use as a credit card or a cash card. Recently, however, an IC card incorporating a nonerasable nonvolatile memory controlled by a CPU built into an IC chip, has been receiving considerable attention as a replacement for the magnetic card, since the greatly increased memory capacity of the IC card over that of the magnetic card makes it possible for the IC card to be used in a much wider range of applications than is possible with a magnetic card. Recently, a multifunctional IC card has been developed which incorporates a battery therein, as well as a keyboard and a display section. This particular IC card, moreover, can be operated in an off-line manner; i.e. without having to be connected to a terminal device or the like.
When this IC card is used as a credit card or a cash card, a transaction valid date, representing a period for which transactions can be made, and a transaction limit amount, representing a maximum amount with which transactions can be made, are set and checked prior to the transactions. These transaction valid date data and transaction limit amount data are stored in a memory of the IC card, and can be externally updated, if desired.
In the conventional case, when the transaction valid date data and the transaction limit amount data are updated, there is no means by which the validity of externally input data can be authenticated. Therefore, the possibility exists that internally stored data may be updated, illegally, for fraudulent purposes. The transaction valid date data and the transaction limit amount data are particularly important data, and these data must not be illegally updated.
Note that the related art for generating a sales approval number on the basis of an input PIN and total amount is disclosed in U.S. Pat. No. 4,697,072 (Inventor: Shigeyuki Kawana, Title: "IDENTIFICATION CARD AND AUTHENTICATION SYSTEM THEREFOR").